Tuning mechanism for electron discharge devices



Jan. 4, 1966 w. PROSKAUER 3,

TUNING MECHANISM FOR ELECTRON DISCHARGE DEVICES IT R l KW N m mm m s R ,E T E w T P R h L m S M T 2 A Filed Oct. 7, 1960 TUNING MECHANISM FOR ELECTRON DISCHARGE DEVICES Filed 001?. 7. 1960 2 Sheets-Sheet 2 llll llll kEllll W. PROSKAU ER Jan. 4, 1966 INVEN TOR. WALTER PROSKAUER k F W @MJXE/Az' ATTORNEYS United States Patent 7, TUNING RECHANISM FOR ELECTRON DISUHARGE DEVICES Walter Proskauer, San Francisco, Calif., assignor to Eitel- McQullough, Inc., San Carlos, Calif., a corporation of California Filed Oct. 7, 1960, Ser. No. 61,246 5 Claims. (Cl. 3155.48)

My invention relates to electronic discharge devices, and particularly to tuning mechanisms for discharge tubes of the klystron type.

One of the important objects of the present invention is the provision of broadband tuning means of a multi-cavity klystron tube in which at least the output cavity is an integral cavity.

Another object of the present invention is the provision 'of a versatile tuning mechanism for a multi-cavity klystron for the production of from 50 to 75 kilowatts of continuous wave power at from 755 to 985 megacycles with at least a 15 db gain.

A still further object of the invention is the provision of a klystron tuning mechanism incorporating eflicient and novel cooling means.

Still another object of the invention is the provision of a tuning means which is movable from outside the evacuated envelope to accurately tune the evacuated output cavity to a selected frequency.

Still another object of the invention is the provision of tuning means enclosed within a vacuum output cavity and having a configuration cooperating with the configuration of the cavity to provide linearity of tuning.

Another object of the invention is the provision of means for effecting movement of a tuning element within an evacuated resonant cavity by digital manipulation of means outside the cavity.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the invention. It is to be understood that I do not limit my invention to the embodiment disclosed, as I may adopt variant embodiments within the scope of the appended claims.

Briefly described, a klystron tube incorporating my invention comprises an electron gun assembly connected at one end to a radio-frequency interaction assembly, including drift tube sections separated by dielectric radio-frequency window sections or conductive walls aligned with the drift tube sections. The radio-frequency assembly has attached to its other end a collector electrode to collect the beam of electrons projected by the electron gun through the radio-frequency assembly. The drift tube sections are axially spaced to provide interaction gaps at spaced intervals along the axis of the tube. The radiofrequency structure is provided with an integral output cavity surrounding the output gap of the drift tube. The electron gun, radio-frequency structure, and collector electrode are integrally and hermetically united to form a vacuum-tight envelope which is subsequently evacuated. The integral output cavity of the tube shown is designed for resonance at the desired output frequency, the range extending from about 750 to 1,000 megacycles. Means are provided within the integral cavity movable from outside thereof to tune the cavity to the desired frequency. Also associated with the output cavity is an output conductor or loop adapted to provide means for extracting electromagnetic energy from the output cavity. Means are provided associated with the tuning means and output loop for the passage of a fluid coolant therethrough. Col lector means are provided integrally united with the output cavity to receive the electrons after they pass the output gap.

3,227,916 Patented Jan. 4, 1966 Referring to the drawings: 4

FIGURE 1 is an elevatiorial view showing the klystron tube incorporating my invention in operating position.

FIGURE 2 is an elevational view, partly invertic'a'l half-section, of a part of the tube and showing the inter" nal structure thereof, including a portion of the tuning mechanism of my invention.

FIGURE 3 is a horizontal sectional View, partly in elevation, taken in the plane indicated by the line 3-3 of FIGURE 2.

FIGURE 4 is a vertical sectional view, partly in elevation, taken in the plane indicated by the line 44 of FIG- URE 3.

FIGURE 1 is drawn to a scale approximately actual size. FIGURE 2 is drawn to a scale approximately actual size. FIGURES 3 and 4 are drawn to a scale approximately /2 actual size.

In terms of greater detail, the klystron tube with which the tuning mechanism forming the subject matter of this invention is associated comprises an electron gun designated generally by numeral 2, and includes, operatively associated within a cylindrical dielectric housing or envelop'e portion 3, electrode elements comprising a cathode 4, a beam-focusing electrode 6, and an accelerating or modulating anode 7, the latter including a centrally positioned coaxially arranged drift tube section 8, and a housing or envelope portion 9 integrally and hermetically united to one end of dielectric cylinder 3. The cathode 4 of the electron gun is preferably of the dish-shaped matrix type and coaxially arranged within dielectric cylinder 3. Each of the electrodes is appropriately provided with an external terminal which may be connected to a source of power.

Operatively associated integrally with the output or downstream end of the electron gun is a radio-frequency structure designated generally by the numeral 12. The radio-frequency structure includes a plurality of axially aligned and spaced drift tube assemblies designated generally by numerals 13, 14, 16, and 17. Drift tube assembly 13 comprises a drift tube section 18, axially aligned with drift tube section 8 and spaced therefrom to provide gap 19, and provided adjacent its ends with integral transversely extending annular mounting plates or flanges 21 and 22. Serving to integrally and hermetically unite the electron gun structure with the radio-frequency (RF) structure is a cylindrical dielectric insulator 23. The insulator is coaxially arranged around the adjacent end portions of drift tube sections 8 and 18 surrounding gap 19, and is integrally and hermetically brazed at one end to modulating anode 7, and at its opposite end is united in like manner to the peripheral edge portion of mounting flange 21. Insulator 23 thus functions to electrically insulate the gun and RF structures, while hermetically uniting them into a composite envelope.

Drift tube assembly 14 may be designated as the intermediate or long dn'ft tube assembly and comprises drift tube section 24 axially aligned and spaced from drift tube section 18 to provide an interaction gap 26. Brazed adjacent opposite ends of drift tube 24 are parallel mounting plates or flanges 27 and 28. To integrally and hermetically unite drift tube assembly 14 to drift tube assembly 13, a cylindrical dielectric RF window 29 is interposed between flanges 22 and 27. Opposite ends of the window are united to the associated annular flanges and brazed adjacent the outer peripheries thereof. As with insulator 23, window 29 functions to mechanically support the drift tube assemblies in axially spaced relationship, and functions also to electrically insulate these two drift tube assemblies against the passage of RF energy from one to the other. A third function performed by window 29 is to provide a portion of the envelope wall. It will be seen from FIGURE 1 that window 29 encloses a chamber between plates 22 and 27 which comprises a portion of a resonant cavity.

Drift tube assembly 16 is axially spaced from drift tube assembly 14 and comprises drift tube section 31, having oppositely disposed integrally united transversely extending annular mounting flanges or plates 32 and 33 brazed adjacent opposite ends of the adjacent drift tube sections. As shown best in FIGURE 2, a cylindrical dielectric Window 34 is integrally and hermetically interposed between flanges 28 and 32. The lengths of the window and associated parts are proportioned to provide an interaction gap 36 between the adjacent ends of drift tube sections 24 and 31.

It has been indicated that insulator 23 and each of radio-frequency dielectric windows 29 and 34 are integrally and hermetically united, respectively, to the associated modulating anode 7 and metallic plates 21, 22, 27, 28, and 32. For clarity of description, the means utilized to form a hermetic and temperature-compensating union will be described only once, the construction being typical wherever required. As shown associated with radio-frequency window 29 and plate 22, the sealing means as indicated generally by numeral 37 comprises a thin metallic flange 38 brazed along one peripheral portion to the metalized end of dielectric cylinder 29. The other end of flange 38 is heliarc welded to the adjacent and juxtaposed end of cylindrical flange 39, the other end of which is in turn integrally brazed to a peripheral portion of plate 22. -A backing ring 41 of dielectric material similar to the material of the associated window 29 is brazed on flange 38 opposite to and axially aligned with window 29 to relieve stresses in the union and form an abutting member against plate 22, which permits relative sliding motion between the parts.

From the foregoing it will be apparent that each of the sub-assemblies of the radio-frequency structure is integrally and hermetically united to each of the other subassemblies in a rigid union capable of withstanding and compensating for expansion and contraction of the parts due to thermally imposed stresses. It will also be apparent that the relationship of the parts, being formed in a cylindrical motif, renders the structure easy to fabricate, thus lessening the cost of the unit.

It is also apparent that mounting flanges 2227 and 28-32 on adjacent ends of drift tube sections 18, 24, and 31 provide a near ideal means for detachably mounting external tuning boxes 42, shown in dash lines in FIG- URE 1. With this detachable type of tuning box in position, radio-frequency windows 29 and 34 define a portion of the resonant cavity Within the evacuated envelope and permit the passage of electromagnetic energy into the external portion of the resonant cavity formed by the tuning boxes. Such tuning boxes are designed for the particular frequency range in which the tube is designed to operate, and are provided with tuning means 43 capable of being adjusted from outside the tuning box. Such tuning means may conform to conventional plunger type means, or to the type tuning means forming the subject matter of this invention. It will of course be obvious that in the event external tuning boxes are not applicable for a particular environment, gaps 26 and 36 may be surrounded by a resonant cavity completely enclosed by plates or mounting flanges 22-27 and 2832 and a metallic wall integrally united with the outer peripheral edges of these plates to provide integral cavities. Where integral cavities are provided, an appropriate tuning means as hereinafter described is preferably included within the evacuated chamber forming the resonant cavity; however, it is to be understood that the tuning means described herein is also applicable in external cavity resonators.

As shown best in FIGURES 2 and 4, drift tube assembly 17 comprises a drift tube section 44 axially aligned with drift tube section 31. Annular plate 45 integrally brazed on drift tube section 44 adjacent one end lies axially spaced and parallel to plate 33 on drift tube assembly 16 and therewith defines a portion of an evacuated integral resonant cavity 46. Drift tubes 31 and 44 are spaced from each other within the cavity to provide an output or working gap 47 therein. To complete resonant cavity 46, conductive walls 33 and 45 are provided with a cylindrical interconnecting conductive wall 48 which encloses and defines the resonant output cavity and provides a conductive path connecting the adjacent ends of drift tube sections 31 and 44 for the passage of radiofrequency current. As shown in FIGURE 2, the inner end portions of drift tube sections 31 and 44 function to provide reentrant extensions of the conductive walls of the cavity resonator and aligned field-free drift spaces. Means are provided associated with the integral cavity thus formed for tuning the cavity to the desired resonant frequency and for coupling energy out of the cavity.

In this preferred form, shown in FIGURES 3 and 4, the tuning means for the integral output cavity comprises a tuning paddle 51, movably interposed between the working gap 47 and the cylindrical wall 48 of the cavity. The end edge of the tuning paddle remote from the working gap is integrally united to a pivotal base plate 52. The tuning paddle extends away from the pivoted base plate in a shallow curved portion 53 having lateral edges capacitively related to the plates 33 and 45, and terminates in a free end 54 lying on the opposite side of the longitudinal axis of the tube from pivot plate 52. As shown in FIGURES 3 and 4, the base plate is pivotally mounted by adjustable conical type bearing pins 56 on integral and inwardly extending lugs 57 formed on the inner end of tuning housing 58. The housing is preferably cylindrical and extends transverse to the axis of the drift tubes. At its end adjacent the lugs 57, the cylindrical housing is provided with shoulder 59 adapted to be integrally and hermetically brazed to wall 48 of resonant cavity 46 about an appropriately positioned aperture, the lugs 57 extending through the aperture past the wall and into the cavity.

The end of the housing remote from resonant cavity 46 is provided with a radially inwardly extending integral annular flange 61, having a large central aperture therein. The aperture in flange 61 is hermetically closed by a bellows 62 having its outer open end 63 integrally and hermetically united to the inner periphery thereof and its inner closed end 64 integrally and hermetically united to the side of pivotal base plate 52 remote from paddle 51. Alternatively, the bellows, pivot plate, and pivot pins may be arranged so that the pivot pins lie outside the evacuated enclosure. Such a cooperative combination may be accomplished by hermetically uniting the open end of the bellows to the wall 48 or to the inner end of housing 58, and the outer end of the bellows to pivot plate 52, repositioned adjacent support or closure plate 66. Pivot pins 56 may then extend between cylindrical housing 58 and pivot plate 52 and lie outside the evacuated chamber defined by the resonant cavity and bellows. It will thus be seen that, with either construction, tuning paddle 51 is permitted to pivot back and forth toward and away from gap 47, that is, transversely with relation to the central axis of the adjacent ends of drift tube sections 31 and 44, and the convolutions of the bellows flex to accommodate such movement. It is thus possible to control the movement of the tuning paddle by means outside the evacuated integral cavity. Such control means include support or closure plate 66 detachably secured to the outer end of the tuning housing by cap screws 67 to provide a rigid but detachable support for the control mechanism. Plate 66 is provided with a bearing aperture 68, and an adjacent access aperture 69. When plate 66 is disposed over the end of cylindrical housing 58, apertures 68 and 69 lie disposed within the peripheral limits defined by the open outer end of the bellows. The apertures thus provide passages for inserting mechanism through plate 66 for attachment to pivot plate 52. Such mechanism includes an elongated extensible stem portion 71 extending through aperture 68. Adjacent its inner end the stem is provided with a threaded bore 72, in which is adjustably engaged a threaded stem extension 73, having a bifurcated lug 74 at its inner end pivotally connected detachably to an integral lug 76 on pivot plate 52. The lugs 74 and 76 cooperate to permit pivotal movement of the stem in one plane, but prevent rotation of stem extension 73. It is thus possible to rotate stem portion 71, provided on its outer end with means for digital manipulation, to control transverse movement of tuning paddle 51.

As seen best in FIGURE 3, the stem is rovided intermediate its ends with an integral shoulder 77 which determines the position of a bearing 73. The bearing surrounds the stem within the aperture 68 and cooperates with bushing 79 therein to provide a permanently flexible joint between stem portion 71 and plate 66. The bushing may be secured in the aperture 68 by a suitable set screw (not shown). To lock the beaing on the stem, a detachable snap ring 82 is provided on the side of the bearing opposite shoulder 77. As shown in FIGURE 3, by providing a peripheral surface on bearing 78 cooperating with a complementary surface in bushing 79, an effective universal joint is provided at this point. Stem portion 71 is thus permitted to rotate about its own axis, which extends transverse to the axis of drift tubes 31 and 44, and is also permitted to move in a transverse plane about bearing '78 as a pivot point or fulcrum, but is prevented from moving longitudinally. Since clockwise rotation of the stem about its own axis will cause the stem extension 73 to become further engaged in threaded bore 72 and cause plate 52 to pivot on pins 56 to swing the tuning paddle outward into its high-frequency position, lug 76 will also swing in an arc about pivot pins 56. This necessitates that stem 71 be capable of moving in a transverse plane when tuning paddle 51 is adjusted.

Rotation of the stem is effected by turning knurled head 83 on the outer end of the stem portion 71, which head is provided with lugs 34 for detachable engagement of a suitable wrench or manipulation with the fingers. It is desirable to prevent the tuning paddle from contacting drift tubes 31 and 44 because to do so would probably melt the paddle as the result of electron bombardment or intense RF current flow, and it is also desirable to keep the tuning paddle from bearing against wall 48 of the resonant cavity to prevent placing a destructive stress on the pivot pins 56. Means are therefore provided interposed between the rotatable portion 71 of the stern and the housing to limit inward and outward movement of the paddle upon rotation of head 83 to prevent the transmission of mechanical stress onto the pins 56 at either extreme of the paddle movement.

Outside the housing the stem is provided with a threaded section 86 adjacent bearing 78, and another threaded section 87 adjacent turning head 83. Intermediate these two threaded sections of stem portion 71 is a section 38 devoid of threads. Threadedly engaging section 86 of stem portion 71 is a guide plate 89 having a central hub 91, from which extend integral guide flanges 92 having slots 93 adjacent their outer ends. The flanges extend on opposite sides of the stem portion, and slots 93 are snugly and slidably engaged by the outer ends of guide screws 94, the inner ends of which are threadedly engaged in plate 66. It will thus be seen that as stem portion 71 is rotated in either a clockwise or counterclockwise direction to manipulate the tuning paddle, guide plate 89 is prevented from rotation by screws 94 working in slots 93, but is permitted to move along threaded section 86 relative to the stem portion. The slots of course accommodate transverse movement of the outer end of the stem portion.

To control outward movement of the tuning paddle toward the wall 48, a stop nut 96 adjustably threaded on section 87 of the stem portion is provided. A set screw 97 in the stop nut, adapted to be jammed against the stem portion, provides means for locking the lock nut in a desired position. The position in which the lock nut will be locked is determined by the extent that it is desired tuning paddle 51 to move. Thus, as shown best in FIGURE 3, space 98 between flange 99 on the stop nut and hub 91 of guide plate 89 may be adjusted to permit a prescribed number of clockwise revolutions of the stem portion to bring the guide plate into jamming relation with stop nut 96. Further rotation of stem portion 71 in this direction is thereby prevented. Conversely, to limit inward movement of tuning paddle 51, a stop washer 101 is adjustably interposed on threaded section 86 between hub 91 of guide plate 89 and snap ring 82. Adjusting the position of washer 101 with respect to hub 91 determines the number of counterclockwise revolutions required to bring the guide plate into jamming relationship with washer 101. When these two elements have been brought into jamming relationship, further rotation of stem portion 71 is prevented, and further movement of tuning paddle 51 toward the drift tubes is terminated. It will of course be understood that if desired the parts may be propotioned so that washer 101 abuts the snap ring and thus determines the inner limit of movement of the tuning paddle.

Because radio-frequency current will tend to flow around the cavity between drift tube tips 31 and 44, there will be a tendency for current to follow the conductive path provided by lugs 57, pivot pins 56, and pivot plate 52. Inasmuch as there is a discontinuous electrical path through the three elements, passage of current therethrough will tend to form an arc and/or heating at such discontinuity. To minimize the passage of current through these elements, means are provided electrically connecting plates 33 and 45 in the area closely adjacent pivot plate 52 to provide a shunt therearound. Such means comprise at least one axially extending conductor rod 106 integrally extending between plates 33 and 45. The conductor rod 106 thus forms a low resistance path between the two plates and prevents radiofrequency current from following the more resistive, path through the pivot points. Because it is subject to heating from electron bombardment, the tuning paddle is preferably hollow to provide for the passage of a coolant therethrough. The tuning paddle is thus preferably fabricated from two shaped plates of copper provided with complementary peripheral flanges 107 adapted to be abutted and brazed to each other in a fluid-tight manner to complete the paddle. A centrally disposed pad 108, in the nature of a peninsula having a connection with peripheral flange 107 at only one end of the paddle, forms with peripheral flange 107 a passage through the paddle for the turbulent flow of a coolant. The passage is proportioned to provide an optimum of turbulent flow for the pressure for which the cooling system is designed. Either water or some other fluid medium, such as a glycol solution, may be used. An inlet aperture 109 adjacent the base of the tuning paddle communicates with aperture 112 in pivot plate 52 to admit coolant into the tuning paddle. The inlet aperture in plate 52 is connected by suitable means such as conduit 113 to a source of coolant fluid. An outlet aperture 114 adjacent the base end of the tuning paddle and on the opposite side of pad 108 from the entrance aperture is provided to permit egress of fluid from the tuning paddle. The outlet aperture 114 is in registry with outlet aperture 116 formed in pivot plate 52. Conduit means 117 connected with outlet aperture 116 carries the coolant away from the tuning mechanism. It will thus be seen that regardless of what position the tuning paddle may be in, coolant fluid may be pumped therethrough to carry away heat.

To couple radio-frequency energy out of integral output cavity 46, means are provided on one wall of the cavity permitting the extension of a coupling loop 121 into the cavity. The coupling loop comprises a copper tube formed into an L shape and having one end with in the resonant cavity integrally and hermetically brazed to plate 33 in registry with an aperture 122 therein as shown best in FIGURE 2. The other end of the coupling loop extends out of the cavity through an aperture 123 formed in wall 48. The outer end of the tubular coupling loop is provided with a plug 126, and apertures 127 extend through the wall thereof at a point spaced from the plugged end of the tube. Apertures 127 communicate the interior of hollow coupling loop 121 with the interior 128 of hollow coolant jacket 129. At its inner end jacket 129 is integrally and hermetically brazed about tube 121 to prevent the passage of coolant into the output cavity except through the hollow loop 121. At its outer end jacket 129 is provided with a sealing flange 131 extending through the central aperture of an annular dielectric radio-frequency window 133. The outer periphery of dielectric window 133 is integrally and hermetically brazed on the interior surface of copper cylinder 134. As shown best in FIG- URE 2, the dielectric window is interposed between the inner and outer ends of cylinder 134. The inner end of cylinder 134 is integrally and hermetically welded to wall 48 of the output cavity by a junction ring 136 and sealing flanges 137 and 138. The union at this point is sirnlar to hermetic seal 37 previously described, with the exception that backing ring 41 is omitted. It will thus be seen that cylinder 134 is coaxially arranged with aperture 123 and the outer end of coupling loop 121. It will also be apparent that cylinder 134 functions as the outer conductor of an integral coaxial transmission line section adapted to be connected to a complementary coaxial transmission line by an annular connecting flange 139, integrally brazed at its inner periphery on the outer end of cylinder 134. An annular shell 141 surrounds cylinder 134 in the vicinity of radio-frequency window 133 in radially spaced relationship to provide a coolant passage 142 about cylinder 134. The outer end of shell 141 is integrally connected in a fluidtight manner to flange 139, while the inner end of shell 141 is brazed about the cylindrical periphery of cylinder 134. Inlet and outlet tubes 143 and 145, respectively, are provided to admit and carry coolant away from the jacket.

Means are provided outside the dielectric window electrically connecting the outer end of coupling loop 121 to provide a connecting means for the inner conductor of an associated transmission line. Such means comprise an annular metallic sealing ring having a generally U-shaped cross section and a diameter substantially equal to the diameter of coolant jacket 129, with the bottom of the U-shaped ring integrally and hermetically brazed to an annular metalized surface on the dielectric window 133 immediately adjacent its inner periphery. The inner flange 147 of the sealing ring lies coaxially arranged and contiguous about the sealing flange 131. By heliarc welding their outermost edges 148, the union at this point is made integral and hermetic. The outer flange 149 is brazed about the outer peripheral portion of a window bushing 151 coaxially arranged with respect to the aperture in the window. As shown in FIGURE 2, the bushing 151 is preferably spaced a short distance from the outer surface of ceramic ring 152 interposed between bushing 151 and the bottom of the U-shaped sealing ring. Ceramic ring 152 forms a backing ring for the sealing ring to prevent rupture of the hermetic union between the sealing ring and dielectric window 133. Positioning bushing 151 spaced from backing ring 152 a small amount permits a measure of contraction and expansion of the parts due to fluctuations in temperature.

From the foregoing it will be apparent that means having a uniform impedance have been provided for coupling energy out of the integral cavity which are at once rigid but which compensate for thermal expansion and contraction and which also provide for the passage of a fluid coolant over elements which experience the greatest fluctuations in temperature. Additionally, it should be noted that the conduction of electromagnetic energy through RF window 133 is elfected at constant impedance. It will, of course, be obvious to those skilled in the art that in the event it is desired to couple a waveguide to the integral cavity, coupling loop 121 can be omitted and window 133 replaced by a window designed to cooperate with an appropriate cavity-to-waveguide transition section interposed between the cavity and the particular waveguide.

Rigidly mounted on the terminal end of the radiofrequency structure is a collector electrode assembly designated generally by numeral 156 and shown in outline only inasmuch as the detailed collector construction forms no part of this invention. The tube shown is designed to have a maximum beam power of 210 kw. and a RF output of 50-75 kw., resulting the collector being required to dissipate at least the energy remaining in the spent beam, which can be as high as kw. Inasmuch as a beam may be projected at a time when there is no RF in the circuit, it is desirable that the collector be capable of dissipating the entire 210 kw. of DC. power in the beam. To dissipate the heat generated by this much power requires a collector of substantial size. Because it is substantial, a difficult problem is posed of mechanically and hermetically attaching the collector electrode to the terminal end of the radio-frequency structure while maintaining the collector electrically insulated therefrom. Such connecting means preferably comprises an annular plate 157 integrally brazed on the terminal end of drift tube 44, and an aperture annular ring 158 having threads on its inner periphery engaging the outer periphery of plate 157. Apertures adjacent the outer periphery of annular plate 158 receive appropriate dielectric bushings (not shown) which permit the passage of bolts 162 binding the collector electrode to plate 158. Dielectric spacers 163 surrounding bolt 162 and interposed between plate 158 and base plate 164 of the collector cooperate to electrically insulate and mechanically bind plates 158 and 164.

Collector plate 164 is preferably of heavy copper-nickel and annular in cross-section to provide a central aperture through which the electron beam may enter into the interior of the collector. Because the collector is axially spaced from the terminal end of the radio-frequency structure, means must be provided to hermetically communicate the interior of the collector to the interior of the radio-frequency structure. Such means are preferably provided by axially aligned dielectric cylinders 168 and 169 connected, respectively, to plate 157 and collector base plate 164. One end of each of these cylinders 168 and 169, which are preferably ceramic, is integrally and hermetically united to the associated plate by means of a seal 37 similar to those previously described. The adjacent metalized edges of the two axially aligned cylinders are integrally and hermetically brazed to an intervening terminal and sealing ring 171, extending into the envelope to provide an inner terminal to which is connected an appropriate gettering structure forming no part of this invention and therefore not shown. The body of the collector comprises a tubular cross-section open at its end adjacent collector plate 164 and integrally brazed thereto. The other end of the collector remote from plate 164 is closed by a suitable cap having an inlet port 188 and an outlet port 192 communicating with suitable passages around the collector body to permit the passage of coolant fluid.

The collect-or, however, is not the only element of a klystron tube which requires cooling. Other elements of the structure closely related to the electron beam are apt to be bombarded by electrons and become hot and therefore require cooling. Such other elements include the drift tube assemblies and the radio-frequency windows associated therewith. To efi'ect such cooling I have provided an interconnected cooling system adapted to provide optimum turbulence in the coolant fluid in contact with the elements which require cooling. Because it is important that the coolant fluid enter the system at or adjacent the point of highest temperature, the system which I have provided preferably admits the coolant to the system through radio-frequency window 133 into jacket 129. It will of course be apparent that in a particular application coolant may be admitted at two or more points in the system and exit at a common outlet. From jacket 129 the coolant flows through apertures 127 and hollow coupling loop 121 into an appropriate jacket assembly surrounding drift tube section 31, shown best in FIGURE 2. As there shown, the coolant enters the jacket assembly through aperture 122 in plate 33 and flows into coolant chamber 201 comprised of outer cylindrical 202 and inner cylindrical shell 203. As shown in the drawing, shell 203 is radially spaced in coaxial relationship to the exterior surface of drift tube 31. A slot in cylindrical shell 203 permits coolant to flow from chamber 201 into chamber 205 provided between inner shell 203 and the drift tube. From this relationship of the shells 202 and 203 it will be seen that inner shell 203 is spaced from the drift tube an amount to ensure the requisite cross-sectional configuration for turbulent flow.

From its point of entry, the coolant flows in a turbulent manner around the drift tube and exits through tube 206 having its inner end inegrally brazed to shell 203 and communicating with chamber 205. Its outer end extends outwardly through chamber 201 in a fluid-tight manner, to be appropriately connected at its outer end by conduit means, shown best in FIGURE 1. As shown, such conduit means comprises conduit 113 communicating with the inlet port of tuning paddle 51. Coolant from. the coolant jacket thus enters the tuning paddle, circulates turbulently through the hollow paddle, and exits througih conduit 117, the other end of which is connected to inlet tube 143 of jacket 141 surrounding the radio-frequency window as previously described.

From this coolant jacket, conduit 144 connects the outlet connection 145 to the inlet of a coolant jacket as sembly surrounding drift tube 44, the outlet of which is connected, in turn, by appropriate conduit means with the inlet of a coolant jacket assembly on drift tube assembly 14.

The outlet of this jacket assembly is connected by appropriate conduit means with the inlet of a coolant jacket on drift tube assembly 13. This jacket assembly communicates through an appropriate conduit with a waste line if the coolant fluid is water, or with apparatus for cooling the fluid if the coolant is some other fluid, such as a glycol solution.

It will thus be seen that maximum cooling efficiency is obtained by admitting the coldest coolant at or adjacent the hottest part of the apparatus and permitting it to circulate turbulently around the tube, progressively encountering those elements which are coolest. It will also be apparent that the integral coolant jacket assemblies, being connected as they are between the drift tube or mounting flanges 21, 22, 27, 28, 32, 33, and 45, lend rigidity to the structure and provide a conductive path for heat to flow away from waveguide windows 29 and 34. It is thus possible to generate a great deal of power with the tube described, and efliciently dissipate the heat which is generated. It will also be apparent that novel means have been provided for tuning the integral resonant cavity, and for coupling energy out of that cavity and into an associated waveguide or coaxial transmission system.

I claim:

,1. In an electron discharge device, a hollow shell symmetrical about a longitudinal axis and defining a cavity resonator, a tuning paddle pivotally mounted at one end on the shell for pivotal movement about an axis parallel to said longitudinal axis and extending into the cavity in a free end capacitively related to the shell, means opertively connected to the tuning paddle and extending out of the shell to effect controlled movement of the tuning paddle within the cavity, and flexible wall means forming a hermetic seal between the paddel and said shell.

2. A cavity resonator comprising a shell defining 'the boundaries of the cavity, a base plate, pivot pin means pivotally supporting said base plate on the shell, a tuning paddle fixed at one end on one side of the base plate and extending into the cavity in a free end capacitively related to the shell, flexible wall means forming a hermetic seal between said base plate and shell, and control means operatively interposed between the other side of the base plate and shell to selectively pivot the plate to effect movement of the tuning paddle.

3. In combination with an electron-permeable cavity resonator comprising an evacuated shell having an aperture therein, a tuning mechanism for the cavity comprising a hollow housing fixed on the shell about the aperture therein, a base plate pivotally mounted on the housing, a tuning paddle mounted on the base plate and extending into the shell and selectively movable therein, a flexible member hermetically interposed between the base plate and the housing to hermetically seal the aperture in the shell, and a control stem operatively interposed between the base plate and housing and movable from outside the shell to effect movement of the tuning paddle within the shell, said control stem includes an axially extensible portion and a rotatable portion, the axially extensible portion being movably connected to the base plate and the rotatable portion being mounted on the housing.

4. The combination according to claim 3 in which the tuning paddle is provided with a hollow interior, the base plate is provided with passages communicating with the hollow interior of the paddle, and conduit means connect the passages to a source of coolant adapted to circulate through the hollow paddle.

5. A klystron tube comprising an electron gun for projecting a beam of electrons, a radio-frequency interaction structure connected at one end to the gun and having a plurality of resonant cavities arranged for interaction with the beam, tuning means associated with at least one of said cavities, and including a tuning paddle pivotally mounted on the interaction structure about an axis parallel to the beam and extending into the associated cavity, flexible wall means forming a hermetic seal between the tuning paddle and the interaction means, a control stem connected to the tuning paddle to effect transverse movement of the paddle toward and away from the beam, and a collector mounted on the end of the interaction structure remote from the gun to intercept the beam after is passes through the interaction structure.

References Cited by the Examiner UNITED STATES PATENTS 2,425,738 8/1947 Hansen 3155.47 X 2,542,797 2/1951 Cuccia 3155.46 X 2,568,325 9/ 1951 Diamond 3155.47 2,656,484 10/1953 Cork 315-521 2,682,623 6/ 1954 Woodyard 315-5.47 X 2,785,334 3/ 1957 Garbuny 3155.46 X 2,945,156 7/ 1960 Arnold et al. 3155.47 2,963,616 12/1960 Nelson et al 315-5.48 X 2,968,013 1/1961 Auld 333-83 2,994,009 7/1961 Schmidt et al. 315-5.48 3,058,026 10/1962 Mann et a1. 315-5.48 3,093,804 6/1963 Larue 33383 3,103,609 9/1963 Zitelli SIS-5.23 X 3,122,669 2/ 1964 Nelson 315--5.48 X

GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, ROBERT SEGAL, Examiners. 

1. IN AN ELECTRON DISCHARGE DEVICE, A HOLLOW SHELL SYMMETRICAL ABOUT A LONGITUDINAL AXIS AND DEFINING A CAVITY RESONATOR, A TUNING PADDLE PIVOTALLY MOUNTED AT ONE END ON THE SHELL FOR PIVOTAL MOVEMENT ABOUT AN AXIS PARALLEL TO SAID LONGITUDINAL AXIS AND EXTENDING INTO THE CAVITY IN A FREE END CAPACITIVELY RELATED TO THE SHELL, MEANS OPERTIVELY CONNECTED TO THE TUNING PADDLE AND EXTENDING OUT OF THE SHELL TO EFFECT CONTROLLED MOVEMENT OF THE TUNING PADDLE WITHIN THE CAVITY, AND FLEXIBLE WALL MEANS FORMING A HERMETIC SEAL BETWEEN THE PADDLE AND SAID SHELL. 